I definitely agree with REB on this, the K400 is a fun phone, sort of an acoustic Grado if that makes any sense 
. Like my SR225, it is fun, not as Hifi as others, but it excels in a certain type of music, when speed and musicality are required 
. If you are not into classical, but love jaz and rock, those two compliment each other very well.
It has at the same time a lot of PRAT / energy and an intimate character, very suited to things like chamber music, baroque ensembles, vocal music or small jazz formations, Folk rock à la Joni Mitchell, ...
Sounstage is,well, good enough, but not its strong point, so symphonic works or progressive rock sound somewhat restricted. Do not try electronica or metal, they sound really ordinary on that
I had the opportunity to compare them to K501, I felt the K400 had the same tight bass, but in much more quantity, equivalent great mids and highs slighly less detailed, less soundstage, but surprisingly more speed and energy : I expected the K501 to be much better phones, but quite frankly they are just different, I am not sure I would trade one for the other (exchange for some time maybe ?).
So in the end, not allrounders but very interesting phones if you like classical or acoustic music, can be had for €60 or so, I paid €80 for a pair in pristine condition, and I think they can hold their own against many in the €200 price range on the right type of music. At the time, i had to choose between a pair of K500 and my K400, and as many said the K400 were more regarded than their bigger brothers when they were AKG top of the line, I pulled the trigger on these and have never regretted this choice.
. Like my SR225, it is fun, not as Hifi as others, but it excels in a certain type of music, when speed and musicality are required . If you are not into classical, but love jaz and rock, those two compliment each other very well.It has at the same time a lot of PRAT / energy and an intimate character, very suited to things like chamber music, baroque ensembles, vocal music or small jazz formations, Folk rock à la Joni Mitchell, ...
Sounstage is,well, good enough, but not its strong point, so symphonic works or progressive rock sound somewhat restricted. Do not try electronica or metal, they sound really ordinary on that
I had the opportunity to compare them to K501, I felt the K400 had the same tight bass, but in much more quantity, equivalent great mids and highs slighly less detailed, less soundstage, but surprisingly more speed and energy : I expected the K501 to be much better phones, but quite frankly they are just different, I am not sure I would trade one for the other (exchange for some time maybe ?).
So in the end, not allrounders but very interesting phones if you like classical or acoustic music, can be had for €60 or so, I paid €80 for a pair in pristine condition, and I think they can hold their own against many in the €200 price range on the right type of music. At the time, i had to choose between a pair of K500 and my K400, and as many said the K400 were more regarded than their bigger brothers when they were AKG top of the line, I pulled the trigger on these and have never regretted this choice.
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